Quantitative data about gametogenesis and embryonic development inHydra vulgarisPall. (Cnidaria, Hydrozoa)

Abstract

This paper reports on the reproductive behavior of gametogenically active polyps of Hydra vulgaris (Pallas, 1766) strain "Scotland 1989" covering an observation period of 4 years . The monitored sexually active hermaphrodites and all their asexually generated offspring produced gametes in uninterrupted series of individual sexual periods, which did not exclude reproduction by budding. Quantitative data are given about the investments made by polyps into gametogenesis in the course of a sexual period. A growing oocyte incorporates more than 10,000 nurse cells (interstitial cells) into the ooplasm by phagocytosis. Various observations suggest that male and female gametes derive independently from separate predetermined stocks of stem cells which are autonomous in their turn from the cell populations committed to somatic renewal processes. Only a small number of the fast and slow developing embryos survived a critical post-hatching period.

Sexual reproduction in the Mediterranean solitary coral Balanophyllia europaea (Scleractinia, Dendrophylliidae)

“…The oral-aboral distribution of Balanophyllia europaea gametogenetic processes is in some ways analogous to that found in other hermaphroditic polyps of freshwater hydras (Stagni 1974, Vannini 1974, Grassi et al 1995, the octocoral Heteroxenia fuscenses (Achituv & Benayahu 1990) and the scleractinian corals Stylophora pistillata (Rinkevich & Loya 1979) and Oulastrea crispata (Lam 2000). Freshwater hydrozoans, and anthozoans, are characterized by the presence of nervous cells throughout their entire body; it has been hypothesized that the neurosecretory activity of these cells is responsible for determining the sexual gonad distribution along the polyp's oral-aboral axis (Schaller 1973, Schaller & Gierer 1973, Stagni 1974).…”

Sex, polyps, and medusae: Determination and maintenance of sex in cnidarians

“…This allows for sex change even in the presence of a male repressive signal and led to the establishment of sequential hermaphroditic phenotypes. Yet, a few Hydra vulgaris strains have been reported that resemble simultaneous hermaphrodites (Grassi et al, ), indicating that sequential hermaphroditism may have been secondarily lost. These models for Hydra phenotypic sex switching provide a framework for future experimentation.…”